Heretofore, modification of polyphenylene ethers (hereinafter, occasionally referred to as PPO) by maleic anhydride has been conducted for the purpose of improving adhesion with inorganic fillers and compatibility with polar resins such as polyamides. As the process for the modification, the modification in a solution and the modification in a melt have been known.
As the modification in a solution, a technology in which styrene, a combination of styrene and maleic anhydride, or a polymerizable polar monomer is grafted on PPO in the presence of a radical generating agent has been known. However, formation of homopolymers and copolymers of the components which are intended to be grafted on PPO and formation of gel in PPO itself inevitably take place in this process. Therefore, when the modified PPO obtained by the process is used in composites and alloys, the composites and the alloys do not have sufficient mechanical properties, heat resistance, or stability. Particularly when the modified PPO is used in composites and alloys containing syndiotactic polystyrene (hereinafter, occasionally referred to as SPS) and the addition of the modified PPO in a small amount is expected to exhibit sufficient effect for improving compatibility with other resins and adhesion with inorganic fillers, the impurities described above cause problems. The use of a solvent causes another problem in that the process becomes complicated and increase in cost is inevitable.
As the modification in a melt, a process in which PPO and maleic anhydride or a derivative thereof are melt kneaded together in the presence of a radical generating agent has heretofore been known. However, PPO has a high melt viscosity, and the melt kneading is substantially possible at a temperature of 300.degree. C. or higher. When the modification is conducted by using maleic anhydride which shows intense irritation and has a low boiling point, deterioration of the working environment caused by vaporization of maleic anhydride makes a great problem. Moreover, when the modification is conducted by using maleic anhydride, the molecular weight of PPO is significantly decreased to result in an insufficient melt viscosity of the modified PPO strands, and this causes a problem in the stability of the production. As another problem, when the obtained modified PPO is used in a composite or an alloy containing SPS, increase in the toughness of the resin composition is insufficient because of the low molecular weight of the modified PPO.
Under the above circumstances, the present invention has an object of developing a convenient process for producing an acid-modified PPO which does not cause deterioration of the working environment, enables stable production, and suppresses decrease in the molecular weight.
The present invention also has another object of providing a resin composition containing SPS which can exhibit a high toughness.